The West Australian Government is under increasing pressure to do more to protect bus drivers from violent assaults.

A 59-year-old bus driver was attacked with a concrete block in Armadale, south-east of Perth, on Friday night.

Police say a group of teenagers boarded the bus, bashed the driver and then threw rocks through the windscreen.

Gerard Sim had emergency surgery and may lose sight in one eye.

The Transport Workers Union says bus drivers in Perth will refuse to work at night unless more is done to protect them from assaults.

The union is attending a meeting with bus companies, police and government officials today to demand safety cages for drivers and more security guards.

TWU bus industry organiser Kevin Starr says drivers are fed up.

"At this stage, we are refusing to work at night without a cage and we'll also be banning any routes that we have a serious incident on - we're considering them banned for the rest of the day - and we'll see how we go the next day," he said.

Mr Starr also wants to see more security guards on buses.

"It has been shown that our response times are too slow and that's only because there are not enough people in place," he said

Tougher penalties

The Opposition's transport spokesman, Ken Travers, says cages are just one measure that should be considered.

"Duress alarms would allow bus drivers to notify their bases if they are suspecting any trouble on their buses," he said.

"Tougher penalties would ensure that idiots that throw rocks and people who assault bus drivers know they will go to jail."

Bus drivers will attend a mass meeting later this week to decide what action to take.